Moistureproof and gas-tight dam for lead-sheath cables



Aug. 26, 1930. REED 1,774,292

MOISTUHEPROOF AND GAS TIGHT DAM FOR LEAD SHEATH CABLES Filed Dec. 2, 1929 ggi inventor 6 J4 jeZandA. Reed (Ittorneg Patented Aug. 26, 1930 UNITED STATES PATENT OFFICE LELAND A. REED, OE NEW YORK, N. Y., ASSIGNOB TO THE WESTERN ON ION TELEGRAPH OI NEW YORK, N. Y., A. CORPORATION OENEW YORK MOISTUBEP ROOF AND GAS-TIGHT DAM FOR 'LEAD-SHEATH CABLES Application filed December 2, 1929. Serial 80.411930.

This invention relates to a method of forming dams in lead sheathed cables at' points where it is desired to sectionalize the cable or at a terminal. s

Such dams are formed in the cable preparatory to making tests for defects in the sheath by introducing gas under pressure into the cable. It isneeessary that each end of a section to be tested shall be closed with lo a gas tight plug- In so far as I am aware no satisfactory method of forming "a as tight 7 and moisture proof dam or closure ad been devised prior to that disclosed by A. Z. .Mample in his application, Serial N 0.

348,346, filed March 19, 1929. The present invention is an improved method of formin the tri-sectional dam described in said appl In the following description I shall refer go to the accompanying drawing in whieh Fi re 1 is a longitudinal view of a cable provlded at intervals with a tri-sectional dam formed in accordance with my invention.

Figure is an enlarged detail view, partly in elevation and party in section illustrating the construction of the tri-seetional dam.

Figures 3 and 4 are detail sectional views illustrating the various steps in the method 7 so of forming said dam in accordance with my invention. V

The cable is constructed of a multiplicity of wires or conductors 6 insulated with a wrapping of paper, the bundle of wires thus 3 formed being surrounded by insulatin paper wrapp1ngs 8 and the wholeencased in a sheath of lead 10.

The plugs or dams, which have heretofore been employed consisted of a single mass of wax introduced v at a high temperature,

usually at 350 F. or higher. In cooling and solidifying there was a certain amount of shrinkage which caused minute crevices to be formed between the wax and the inner wall of the sheath. Even if a tight joint could be secured when the plug was first formed, the continual expansion and contraction induced by changes in atmospheric 60 temperatures soon destroy the'integrity of solidifying, due to definitely. Instead of introducing a wax at a temperature. considerably above its melting point, the outside members of the Mample tri-sectional dam are formed by intro ducing into the cable under pressure, a wax or other sealing material at a temperature only slightly above its melting point. The contraction, if any, is exceedingly slight in the comparatively small change in temperature in cooling and this is offset by thepressure to which the wax or other sealing material is subjected while it is being inserted. Hence 'the initial shrinkage heretofore manifested in the leakage of the plugs is thus overcome." Nevertheless the continual expansion and contraction of the sheath tends to produce crevices between the sealing material and the sheath. This difficn lty has been entirely eliminated in the Mample dam by the introduction of a semiliquid filling between the end plugs which permeates any crevices that may develop and also saturates the paperinsulation on the wires.

In the Mample tri-sectional dam, the end plugs of wax or other sealing material were first introduced through separate openings,

in the sheath after which the semi-liquid sealing medium was inserted 12. The first step in my method or process.

is indicated in Fig. 3. The wax or other sealing material 14 is warmed to a temperature slightly above its melting. point and forced into the 'cable with a pressure gun 15 which may be of the type employed in through a cen- ,tral opening. I have devised an Improved forcing lubrication into the bearings of machinery. The wax in this condition while under pressure will penetrate the core of the cable, permeating the paper insulation and closing all crevices for a distance of approximately two feet on both sides of. the opening in the sheath; .The sheath is slightly warmed or heated depending on the temperature prevailing at the time the dam is made in the cable.

After the wax or other sealing material has solidified, there are numerous small spaces and openings in the solidified material due principally to contraction of the material duringthe cooling. In order to completely fill these openings 'or crevices, the central portion is slightly heated by applying heat from a suitable source. as indi cated at 17, until it has liquefied, as inclicated at 14. The semi-liquid sealing compound 16 is then forced through the open-. ing 12 under considerable pressure by means of the pressure gun 15, whichv forces the liquefied sealing compound into whatever openings or crevices are existing in the still solidlfied end sections, compressing the central zone of melted sealing ,material and causing it to commingle at either side with the softened sealing material to form an in- Wlll be forced toward the opposite side and will eflectually seal any crevice or weak spot in the other solidifiedend portion. In this manner the tri-sectional dam is effective at all times against the passage of gas or moisture...

I claim: v

1. The process of forming a moisture proof seal or dam in a lead gas-tight and heat to soften an intermediate portion of said wax or other sealing material, forcing a semi-liquid insulating compound through said aperture under pressure into said softened intermediate portion to displace the same and c osing said aperture.

3. The process of forming a gas-tight and' moisture proof 1 seal or dam in a lead sheathed electric cable, which consists in cutting a small aperture in the sheath, introducing therethrough a wax or other sealing material which is heated to a temperature slightly above its melting point, permitting said sealing material to solidify, applying heat to soften an intermediate portion of said sealing material, forcing a semi-liquid insulating compound through said aperture under pressure into said softened sealing material to displace the same and closing said aperture.

In testimony whereof I affix my signature.

LELAND A. REED.

sheathed electric cable, which consists in Y cutting a small aperture in the sheath, in-' troducing therethrough'melted wax or other sealing material, dis lacing an intermediate portion thereof by orcing a semi-liquid insulating compound through said aperture under pressure, thereby forming a tri-se'ctional dam and closing said aperture.

2. The process of forming a gas-tight sheathed electric cable, which consists in cutting a small aperture inthe sheath, introducing therethrough melted wax or other sealing material, permittingthe-wax or other sealing material to solidify, applying I and moisture proof seal or dam in a lead 

